The present invention relates to scanning optical systems and, more particularly, to a compact scanning optical system comprising a combination of a deflecting mirror and a reflecting optical system, which is suitable for various uses, e.g. information reading, information recording, and measurement.
Japanese Patent Application Unexamined Publication (KOKAI) No. 11-84291, which was proposed by the present applicant, discloses a scanning optical system comprising a combination of a reflecting optical system having a reflecting surface formed from a rotationally asymmetric surface having only one plane of symmetry, e.g. a free-form surface, and a deflecting mirror, e.g. a polygon mirror.
Japanese Patent Application Unexamined Publication (KOKAI) No. 10-123449, which was also proposed by the present applicant, discloses a compact scanning optical system of the type described above, which uses a deflecting mirror arranged in the form of a micro-mirror device by using semiconductor manufacturing technology.
Incidentally, it is desirable from the viewpoint of obtaining a compact scanning optical system, particularly a thin scanning optical system, to arrange the optical system so that the central beam of the incident light beam and the central beam of the scanning light beam are approximately on a straight line or approximately parallel to each other. However, such an arrangement has not yet been proposed in conventional scanning optical systems using a deflecting mirror, e.g. a galvanometer mirror or a polygon mirror.